This invention relates to the use of microwave antennae for duplex communications and radar.
Duplex communications (reception and transmission) through a single antenna requires separation of the transmitted and received signals, both for the protection of the sensitive receiver circuitry, and to prevent the transmissions from interfering with reception in (simultaneous) full-duplex applications.
When the duplex transmissions are sufficiently different in wavelength, diplexing or filtering can provide ports, each of which couple energy of primarily one channel. The degree to which power of the one wavelength is prevented from coupling to the port that is primarily for a different wavelength is termed its isolation.
Polarization can be used to separate receive and transmit signals.
In time division duplexing cases, where transmission and reception are not simultaneous, switchable attenuation can be provided between the receiver and the antenna.
Combinations of these methods can be used. For instance, separation in frequency and polarization can be employed where a single method is incapable of the desired isolation.
Otherwise, two antennae must be used for duplex operation, in which case both antennae must be aligned with the distant terminus of communication. Whereas an antenna connected to a receiver can be aligned by monitoring the received signal level, antennae not connected to receivers are more difficult to align for optimum performance.
The present invention integrates multiple antennae as a single rigid assembly guaranteeing alignment between these antennae and providing higher isolation with lower insertion loss than single antenna duplexing methods can achieve.